[gnome-software] trivial: Initialize subcategory filter button in category page

[Joaquim Manuel Pereira Rocha <jrocha src gnome org>]

commit 2668a3f2f2be6a72234699dc692a7f2362479854
Author: Joaquim Rocha <jrocha endlessm com>
Date:   Fri Oct 6 12:28:35 2017 +0200

    trivial: Initialize subcategory filter button in category page
    
    The mentioned button had not been initialized which could cause an
    illegal memory access.

 src/gs-category-page.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/gs-category-page.c b/src/gs-category-page.c
index 32fc12c..51cf3db 100644
--- a/src/gs-category-page.c
+++ b/src/gs-category-page.c
@@ -404,7 +404,7 @@ static void
 gs_category_page_create_filter (GsCategoryPage *self,
                                GsCategory *category)
 {
-       GtkWidget *button;
+       GtkWidget *button = NULL;
        GsCategory *s;
        guint i;
        GPtrArray *children;